1. Technical Field
The present disclosure relates to a self leveling shock absorber, and more particularly, to a self leveling shock absorber with a relief valve positioned to prevent the relief valve from escaping and securely maintain an assembling condition of a pump rod.
2. Description of the Related Art
In general, a shock absorber is a vibration-proof or shock absorbing device installed between a vehicle body and an axle to absorb vibrations or shocks transmitted from a road surface to the axle when the vehicle is driven and thus to improve a ride comfort. This shock absorber rapidly absorbs vibrations of a spring generated by a road surface when the vehicle is driven to ensure the handling stability of the vehicle and provide the ride comfort.
In addition, as a technique for a shock absorber has been developed, the aforementioned shock absorber has a function of keeping a vehicle height substantially constant regardless of the number of passengers or weight of baggage as well as absorbs shocks exerted on a vehicle. Such a shock absorber is referred to as a self leveling shock absorber.
In the meantime, an inside of the self leveling shock absorber is divided into a high pressure chamber and a low pressure chamber, and vibrations are absorbed by damping force generated by oil flowing in the high pressure chamber and the low pressure chamber.
FIG. 1 is a cross-sectional view of a self leveling shock absorber according to a prior art.
As shown in FIG. 1, a conventional self leveling shock absorber 1 comprises a base shell 10, an inner tube 12 installed in the base shell 10, and an outer tube 14 installed between the base shell 10 and the inner tube 12 in a longitudinal direction.
In addition, the self leveling shock absorber 1 comprises a rod guide 16, a hollow piston rod 20, a piston valve 30 and a body valve 40 which are assembled to the inner tube 12, a pump tube 21 and a pump rod 22 which are installed in the hollow piston rod 20, and an inlet valve 23 and an outlet valve 24 which are respectively provided toward one end of the pump rod 22 and one end of the pump tube 21. Also, a pump chamber 25 is defined in an empty space between the pump tube 21 and the pump rod 22.
The piston valve 30 divides an internal space of the inner tube 12 into a rebound chamber 13 and a compression chamber 15 and controls the oil flow between the rebound chamber 13 and the compression chamber 15.
A low pressure chamber 11 to be filled with oil is defined between the base shell 10 and the inner tube 12, and a gas chamber 18 and a high pressure chamber 19 that are separated by a diaphragm 17 are provided between the base shell 10 and the outer tube 14, wherein the high pressure chamber 19 is compressed by the gas chamber 18.
Upper and lower ends of the diaphragm 17 are restrained by an upper holder 17a and a lower holder 17b installed between the outer tube 14 and the base shell 10. In addition, installed to the upper holder 17a is a relief valve 35, which returns oil of the high pressure chamber 19 to the low pressure chamber 11 to maintain the pressure in the high pressure chamber 19 when the pressure in the high pressure 19 is excessively increased.
However, in the prior self leveling shock absorber of FIG. 1, since the relief valve 35 is press-fitted into the upper holder 17a, there are problems in that the mounting space is narrow and the relief valve 35 may escape from the upper holder 17a when high pressure is instantaneously generated.
Further, in the conventional prior self leveling shock absorber of FIG. 1, the pump rod 22 is assembled to the body valve 40 and a fixing member 45 is then press-fitted into the body valve 40 in order to prevent the pump rod 22 from escaping. In this structure, however, it is apprehended that the fixing member 45 may escape during the use of the shock absorber.